. "3 Previous Analyses and Experience with Wingtip Modifications on Existing Aircraft." Assessment of Wingtip Modifications to Increase the Fuel Efficiency of Air Force Aircraft. Washington, DC: The National Academies Press, 2007.
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Assessment of Wingtip Modifications to Increase the Fuel Efficiency of Air Force Aircraft
Boeing 7-Series aircraft have been manufactured by the “heritage” Boeing Commercial Airplanes Company in the Seattle area. The first in-production winglet produced by Boeing was for the 747-400, an improved Boeing 747 introduced in the late 1980s. The wingtip modification introduced on the 747-400 included a 6-ft per side wingtip extension and a canted 6-ft per side highly swept winglet (see Figure 3-1). The purpose of the wingtip modification was to improve the cruise aerodynamic efficiency of the airplane and, to a certain extent, differentiate the -400 model of the 747 family from the earlier -100/200/300 models. The tip modification increased the cruise L/D approximately 4 percent (less than half of the upper limit of 9 percent suggested by wind tunnel tests in the ACEE program, see above), with much of the improvement coming from the span extension. The L/D increase gives an equivalent increase in fuel efficiency.
Boeing introduced the 737 Next-Generation (NG) aircraft in the late 1990s without a tip device. Several years after entry into service, the Boeing
FIGURE 3-1 Boeing 747-400 with swept, canted winglets. SOURCE: Reproduced by permission of Boeing.